His accent comes from somewhere in the mid-Atlantic, masking his Hertfordshire roots. In his own words, the way he speaks "tells you that I am not a normal English person. My passport is European British."
In his 10 years as chairman and chief executive of ICL, the UK computer company now owned by Fujitsu of Japan, Mr Bonfield has gained a reputation as a determined and sometimes ruthless manager.
His easy-going and bantering manner hides what is regarded as an iron will when it comes to business matters. He admits to being sometimes insensitive and "ruthlessly persistent", but those who know him also regard him as scrupulously fair and "very straight and open".
One ICL insider said: "He has a deadpan sense of humour. He is very charming in a curious sort of way."
Mr Bonfield once claimed that much of his approach to life started with the strict discipline imposed by the nuns at his convent school. That could be one reason why he still looks and is extremely fit. He runs every day in spite of the heavy work schedule.
The new BT boss is an engineer who joined Texas Instruments after graduating from Loughborough University. It was with TI in Texas that he met his wife Josephine and developed his love of American life to which he is determined to return.
"My long-term personal goal has not changed. I do enjoy the States and I do have strong links there. If you ask me whether I imagine retiring under a palm tree then the answer is yes - but in the meantime I have to earn a living," he said.
His arrival at BT has been under negotiation since spring. The new job will mean some diminution of other roles. Although he intends to stay on the board of ICL, Mr Bonfield must now consider his part-time posts, including those of non-executive director of BICC and Zeneca.
It is, as he said, ''a very big job".Reuse content